The objective of the proposed research is to define the role of certain environmental influences in terms of their ability to affect the systemic arterial pressure of rhesus monkeys. The hypothesis to be tested is that both the amount of work, in terms of the response rate, demanded to satisfy a coping response and the degree of uncertainty involved in the basic discriminated avoidance schedule will be directly related to acute and chronic elevation of arterial blood pressure. Hourly measurements of blood pressure and heart rate will be made with chronically indwelling arterial and venous catheters in the monkeys restrained in primate chairs. Cardiac output and blood volume measurements will also be made intermittently. These data should have value both in terms of their extrapolation to the environmental situations analogous to those occurring in humans and in determining the most efficient way to produce a laboratory model of hypertension. The results will also help to confirm or deny the role of environmental stressors in the development of hypertension.